metal ions binding study on human growth hormone by isothermal titration calorimetric method

the interaction of hgh with some metal ions ( ) at 27°c in nac1 solution, 50 mm was studied using isothermal titration calorimetry. there is a set of three identical and non-interacting binding sites for binding of all these metal ions, expect . the intrinsic association equilibrium constants () are not very different for  and , and also their molar enthalpies of binding (kj/mol for  and  kj/mol for ) are similar showing same thermodynamical properties for hgh upon interaction  with both  and . thermodynamical properties for hgh upon interaction  with both  is completely different from those of  and . the affinity of binding is the highest (), but the molar enthalpy of binding is the lowest () for  . there is a set of four identical and independent binding sites for . the binding process for iron ions is more exothermic (kj/mol) than other three metal ions and with a higher affinity () respect to and